| 摘要 |
PURPOSE:To obtain reducing copies with a variable power projection optical system of small and economical size by providing a lens array, where minute lens systems are so arranged that the inclination is increased according as going toward both end parts, and high-refractive index transparent body whose thickness is successively increased according as going from the center to both end parts in the slit longitudinal direction. CONSTITUTION:A reduction optical system 34 consists of the first pair of lens elements 36 and the second pair of lens elements 38 of an array similarly to an unmagnification optical system. An objective lens element 44 is placed at the middle point of the scanning array and its optical axis traverses an original surface 40 and an image surface 42, and a relay lens element 46 is optically arranged for the objective lens element 44. According as lens elements are spread outward from the middle point, the inclination of optical axes of lens elements to the optical axis of the lens element at the middle point is increased. Since it is necessary to place high refractive index media on respective optical paths for the purpose of maintaining the same optical path relations in all of the range, optical path compensating plates 52 and 54 having aspherical surfaces are provided. Thus, the variable power projection optical system of small and economical size is obtained.
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